Could someone that knows a heck of a lot more than me explain this "Smart Grid" I keep hearing about? I understand the need to upgrade power delivery systems but I also understand that by delivering smart grid power to homes it will also allow information to flow from the homes.

For example if who ever is in charge ( let's say a socialist government for example) decides that they don't want you doing laundry at 2:00pm they will double or triple your power rate. They will be able to monitor or control when you eat, sleep, use the internet and what you use it for. The implications are terrifying. Or am I possibly over reacting?

The biggest problem in electric grid usages is what's called Starting loads. Usually the big issue in an grid is the Amps available. That is the load, or amount of voltage required to run an electric device. Lets say you have an electric washing machine. its rated for 10 amps of 110 V current. That means it will pull ten amps of power when just sitting there agitating. However, that few seconds when the motor has to start that cycle, and is getting all that stationary water, tub, clothes etc, into motion, that motor may very well draw up to 40 amps. Now the system has no trouble supplying that extra 30 amps, as long as there are not 111000 households all starting that load at the same time. IF that same starting load was applied to those households, that would equal a quadrupling of the power needed.

Now some simple house hold devices are the really big power eaters on start up.. A/C's, Fridges, water heaters and some other appliances can really eat the amps on start up.

A smart grid, uses a signal wave sent via the regular electrical transmission to spread the loads between houses ONLY at peak power consumption times . A switch box is installed that is coded by the power utility to react to a certain code, which stalls the starting time of lets say an A/C for a few seconds, until the grid is ready. When your thermostat calls for the AC to kick on, it asks the box if its ok, and if the box says NO it then waits for a bit until the box receives the "ok its your turn" signal, which then allows your AC to cycle, drawing that 60 or more amps for a few seconds until it settles down to its 15 amp run rate. Its my understanding that with the slow starts system offered here by Xcell will only delay that onset of cooling up to six minutes, and will even out the current pulls dramatically .

Cooooool. I could see how it could be abused once in place. That six minutes could turn into 10, or 20, or 60.

And so will begin DRM style hack/patch battle. Prediction: Signal Filters on ebay for $5

I was going to post something on this, then I realized it wasn't power, it was Heat/AC.

California was proposing requiring smart thermostats that the state could control.

Yeah, and its easily overridden if you need to. just reach over and pull the lever.

THis is not a means of the Govt entering your home...

this is one version, there are others out there

http://www.xcelenergy.com/Residential/P ... witch.aspx

But I want my toast when I want my toast.

realistically, rational code rewritting in the building and trades could cut the US demand for energy in half.

Frankly no new home should be stick built, but built with engineered walls or SIPS systems, the savings in construction costs, material costs, and the costs of retrieving those resources to build conventionally would tally in the Billions almost immediately.

I have built SIP houses from kits that have used less than $40 dollars a month in heat costs and less in cooling. One that I built has had the furnace go on twice in three years, they use a wood fired massive stone heater that requires one burn a day, but is only used when its below 20 degrees, other wise you have to open a window. on days about 30 and above, the surplus heat from cooking, fridge, water heater and other appliances keep the house well heated.

http://www.sipsupply.com/learn_about_sips.html

In their descriptions they are talking about 4.5 inch walls, we regularly build with 10 inch walls and 16 inch thick roof panels. Using German H windows, we get VERY low losses from them and can build that house for very nearly the same cost as a comprable stick home. the fact that its ready in 30 days from starting with a complete foundation often makes up the difference.


While not build by us, our supplier had two houses go thru tornadoes and survive far better than surround conventional built homes.


Often these homes can be built with active and passive solar systems built in, and when done right, are often net earners on the grid with monthly checks from the power company.


Solar Edison LLC is the one good source for this, they also have a good product out for any building over 20K in flat roof, where it will earn you money over 20 years of hte contract, and provide your heat and power at a flat rate guaranteed over those 20 years.


IF we had builder and engineers writing the codes instead of Neighbor hood activists and politicians, huge gains could take place for little or no added cost.

Dean, it has nothing to do with small appliance usage, and if it bothers you that much, learn how to do it with a torch.

I thought my toaster was the thing causing my breakers to trip. I guess you are right, that is a constant draw. It's probably my refrigerator compressor turning on that trips the breaker.

Interesting stuff 1911

Bit of a hijack, but relevant.



1911fan,

You seem to be quite knowledgeable on the subject of electricty. Couple of questions.

If...
Voltage=Electromtive force=Actual power...measured in Volts
Current=Rate of flow of voltage.... measured in Amperes

Then wouldn't the machine actually be pulling 110 voltage at a rate of 10 amps?

Then too, wouldn't the power grid issues be the amount of voltage available, not the rate at which the voltage can be delivered?

As my limited understanding of the power grid goes, you also have the problem of extra voltage needing to be sent "down the line", like at night when there is less consumption. Whereas during the day, somewhere on the line may be calling for more voltage at a higher rate of flow(current) than is currently available, therefore creating a "brownout" or "blackout" down the line.

Just wanted to understand better the knowledge you can share.



MM

What you describe for motor starting current is absolutely correct, but that's not what the utility is trying to control. Once you take into account the load diversity in a neighborhood, the start up of all those A/C units and refrigerators will naturally even out....there's no need to intervene for that. Individual motor startup is just not an issue for the grid. Also, resistive loads (heater loads) such as water heaters do not have an inrush or a start up current. You only get that with motors or transformers.

I think the part of "smart grid" technology you're referring to is demand control. This does control startup of the A/C unit and electric water heaters (in a residential setting) but it's not because of the starting current, it's simply so the utility can shut down 1/4 of those loads at a time. Our A/C unit is on demand control and during peak load days, they can shut it down for up to 15 minutes per hour when normally it might be running not stop. It's not saving the grid from the startup current (which, because of load diversity it won't see) but from the load itself.

Motor inrush current is mostly reactive, meaning it does not consume much power, but mostly VARs (Volt-Amps Reactive), so there is very little increased energy requirement for starting motors.

Now when motors run, they still consume VARS, but a lot less than what they need when starting. The amount they need is indicated by the rated Power Factor. A typical large 3-phase induction motor operates at about a 0.85 power factor. What this means is that only 85% of the current drawn is because of the power requirements of the motor. The other 15% is just using up the system's capacity to supply current and is not being put to real use.

Where VARs come in to play with power transmission is that same issue of line capacity. VAR consumption cause there to be more current on the transmission lines than there would be just due to the power consumed by the load, but since VARs is not the same as power, you do not save energy (except for the decreased line loses) by reducing VARs. What you get is an increase in the capacity of those transmission lines. In the plant power systems I design, I try to get the power factor of the plant to 0.95. This is done mainly by adding capacitors to the system because capacitors create VARs (they're also a maintenance headache but that's another issue). It can also be done by putting the motor on a variable frequency drive but I don't do this unless the process variable speed.

If you're a 3-phase customer, you will actually get penalized by the utility if your power factor is too low because of the line capacity reduction. Depending on the utility, they start charging extra if you drop below 0.95 to 0.90.

The plants I design are often put on a demand control system. On peak days, the plant will drop off the grid and run on their own generator. The plants get a steep discount for doing this, but if for some reason they screw up and stay on the grid, they get penalized big time. One screw up can cost you most of a years worth of benefit in some cases.

Back to the topic, the "Smart Grid" is not one technology, but many that work to reduce demand, allow an easier means for smaller, alternative power sources to get on the grid, increase efficiency, and even power storage technologies.

On a residential level what you'll probably see is the demand control situation described above, but that's not to say that there won't be requirements for the technology to be implemented in appliances themselves that would allow the utility to prevent you from operating certain appliances during certain times. Tied into that there could conceivably be some information going back. I could see, say, preventing washing machines and dishwashers from operating during the day. That would help out the water treatment plants tremendously as well. Not that I support this, mind you.

Sorry for rambling but this is right up my alley.

i have had it explained that the voltage is the size of the "hose" and the amperage is the "Pressure" or volume of voltage. maybe not the whole scientific way, but I know thats how it gets explained everytime we have this issue come up with homeowners.

I have a multi meter. I clip it on my table saw and click it to voltage and the number will hit what ever the wall outlet will supply, 110, 120, what ever the area runs one. I flip it to amps and start the saw from a dead stop, it will reach 38 amps for about 2 seconds, then fade off to about 4 amps, running free. Now if I take a 8/4 hard maple board. (that's 2 full inches of wood) and start cutting I can move that amp meter jump from 4 to about 15 amps pretty easy. At that rate the saw is working at its rated capacity. If I shove harder on the board, or if my blade is dull and it pulls instead of slices, its easy to run that ampmeter up to about 25 or so where the thermal breaker on the saw pops, stopping to motor before I over heat and cook the windings.

my understanding of brown outs are that the hose has too many sprinklers running all at once and the supply is not enough to run them all at the capacity they want to run at. whether this is volts, amps or watts, I don't know. but its a lack of capacity. I don't think you want more voltage going out, as if you run appliances at higher voltages funny things happen, but I think you need more capacity (and forgive me if this is wattage or amps) and the capacity has to be there immediately at the demand because its not like water pressure where you have a stored volume of water in a tower waiting to take up the slack. Any power you are using to read this on your screen, was just generated RIGHT NOW and never existed until you needed it.

Brown out are what the saver switches and smart grids are to prevent. By giving the powerstation a controlled need for power over time versus spike after spike after spike, all mixed with periods of varying length of low power needs.

Compare it to driving a car on road with a thousand stop lights. you need to average 20 miles an hour or your car will crash. One driver hits every stop light, has to come to just about a complete stop just then the light turns, and then he has to FLOOR it to make up the time, and just when he makes his average, the light changes and he has to slow down to just about a stop when the light goes green and he has to slam the pedal down and get back up to speed. Now the second car has a saver switch, he hits twenty MPH, and rolls along, just when he is going to have to slow way down, the saver switch sends a signal and flips the light, allowing the driver to just nudge the gas to be back at 20 MPH. this happens a thousand times an hour. Which car is going to be in better shape, which car will be running more efficiently and which car is going to suffer the fewest accidents and breakdowns?

Black outs are a complete shut down. they can happen for literally thousands of reasons, and at several hundred points along the grid.
Any physical disruption of the wires, from trees falling to balloons in the wires to cars hitting the poles can stop the current from there down the line. While grids are nice ways of calling the layouts, the description also shows the redundancy that is built into the system. if one link is broke, the grid usually can be routed around so that only the immediate area of the disruption is out of juice. I am sure there is someone here far more skilled at this end of the stuff, like Frank (RET) who is a electronics tech who can describe the small stuff better.

But as one who has personally blacked out a few thousand homes, I think I understand that concept.

Voltage does not equal power. To use a plumbing analogy, voltage is like water pressure while current is like water flow. You can shut off a valve to stop the water from flowing but you still have water pressure. Just like you can shut off your coffee pot, but you still have voltage. There is no power unless you have voltage and current, just as there is no water used unless you have water pressure and flow.

Your machine in question would be consuming 1100 watts of power (110v x 10A, and disregarding power factor). Like water pressure, there's no "pulling" of voltage or sending it down the line. It's there whether your drawing current or not. Same thing with transmission lines. The voltage is there whether there's current flowing in the lines or not.

The nominal voltage of transmission lines, distribution lines, and your outlets is fixed. When you talk about "extra voltage" at night, I believe what you're referring to are the affects of line loses. Because transmission lines have resistance, they consume power (given off as heat) and there is a voltage drop from one end to another, as long as current is flowing (like head loss in my water pipe analogy...there is no head loss if there's no water flowing) The greater the current, the greater the voltage drop (and the greater the head loss, the greater the water pressure drop). Now if we have such a high current on the line that the voltage on the far end is too low, I can raise my voltage on my end to compensate for the voltage drop. A problem can come up if the drop is great and I don't have a means to automate changing the voltage, either through a automatic load tap changer on the substation transformer (which changes the secondary voltage), or an automatic voltage regulator. In that case I have to pick a voltage that might be a bit low during the day so it's not too high at night (when there's a lot less demand for power so less current, so less voltage drop). Typically the utility will keep the nominal voltage at the end user to +/- 10%.

Now the main reason for transmitting power at such a high voltage is that because Power = Voltage x Current (ignoring power factor), if you double the voltage, you can cut the current in half, which has the effect of decreasing the line losses by 75% (when using the same wire). Increase the voltage ten fold and you can decrease the current ten fold, which decreases the line losses by 99% (again, using the same wire). This is because the line losses are equal to the wire resistance times the square of the current (I^2 x R).

In practice, though, we reduce the wire size because of the decreased current and since a smaller wire has increased resistance, it brings the line losses back up somewhat, but not near as much as there would ahve been. Utilities optimize all that to get the cheapest system, in terms of lifecycle costs.

I think we have some transmission lines in the US that are in the 750,000 volt range or higher. The distribution line that feeds the transformer that feeds your house is usually in what we call the 15kV class, which can be 12,470V, 13,200V, or 13,800V.

We use this same principal in industrial plants. The larger the load, the higher the voltage. Common voltages are 480V for smaller facilities or 4160V for larger facilities. I have done design for some facilities that have 13,800 volt motors as well.

Brownouts are caused by a reduction of the voltage on the grid, and are fairly rare. A generator has a certain current capacity at rated voltage. You can exceed this current capacity to some extent if you decrease the output voltage below the rated voltage.

If the load on the system is so great that all the generators are pushed past rated current, then they have to decide whether to having rolling blackouts, where demand is decreased by rotating areas on and off the grid, or they can operate for a while below the rated voltage. Operating this way can be damaging to a lot of equipment, particularly motors. I've been out of the power generation industry for about 13 years now, and I didn't work on transmission design, so I can't say if brownouts are ever intentional or not.